Carbonaceous gases such as those disclosed above can be naturally occurring, or can be produced as a byproduct from any of a wide range of industrial processes. Such gases typically comprise various light-end hydrocarbons such as, for example, ethane, methane, ethylene, propane and/or butane in various combinations, depending upon the particular source. In situations where the quantities or compositions of the gas are not sufficient to justify the use of gas-recovery techniques, such gases have in past times either been released to the atmosphere or flared. Releasing these gases to the atmosphere is undesirable because of the dangerously explosive accumulations or pockets that may result. Flaring reduces the risk of explosion, but may still result in undesirably high levels of pollutants, particularly particulate emissions, being released to the atmosphere. Furthermore, flaring carbonaceous gases results in the loss and waste of the carbon which they contain, and is illegal in most jurisdictions.
Generally speaking, the term "carbon black" includes any of various finely divided forms of carbon made by the incomplete combustion or thermal decomposition of a carbonaceous fuel. The principal types of carbon black, classified according to the method of production, are impingement black (also frequently referred to as channel black), furnace black and thermal black. Impingement black is generally characterized by a lower pH, higher volatile content and less chainlike structure between the particles. Impingement black has the smallest particle size and largest specific surface area of any industrial material. Particles of impingement black are typically in the colloidal range, with surface areas running to about 18 acres per pound. High quality impingement blacks are sometimes referred to as "special blacks." The uses for special blacks recovered from gaseous hydrocarbons are numerous. Such blacks are used, for example, in the manufacture of inks, plastics, pigments, wire insulation, photocopying, and the like.
Methods and apparatus for producing impingement black from carbonaceous gases have previously been disclosed, for example, in U.S. Pat. Nos. 2,427,509; 3,051,554; and 3,987,019. The previously disclosed methods and apparatus for producing impingement black have utilized the exterior surfaces of channels, discs or drums as the impingement surfaces. Burners disposed near the impingement surfaces are fueled with a carbonaceous gas and an amount of oxygen which is sufficient to support combustion but insufficient for complete combustion of the carbon contained in the gas, thereby causing such carbon to be deposited as carbon black on the surface against which the flames from the burners impinge. According to conventional methods and apparatus, the carbon black is thereafter recovered when the impingement surface is withdrawn from the flames and scraped, causing the carbon black to fall from the surface into collection hoppers by gravity flow. However, numerous disadvantages have been encountered in using the devices previously disclosed.
With some of the devices, temperature control and the dissipation of heat have been a problem. If the impingement surface becomes excessively hot, the yield of carbon black deposited per given volume of gas will decrease. Moreover, undesirable expansion or warping of the impingement surface may occur. This is particularly true in apparatus utilizing metallic plates as the impingement surfaces.
Another disadvantage relates to the method and apparatus used to collect the carbon black deposited on the impingement surface. The scrapers and gravity-flow collection hoppers employed in the conventional devices require that the impingement surface be disposed above and closely adjacent to the collection hopper, a limitation that may be inconvenient or unworkable for some applications.
A further disadvantage relates to the fact that apparatus conventionally employed for the production of impingement black have not been adapted for ease of transportability, installation and subsequent relocation to another use site. The provision of an efficient mobile carbon generator would greatly facilitate the recovery of carbon on a cost effective basis from sources of carbonaceous gases that were previously considered to be either too small or too remote to warrant such treatment.
The prior art suffers the further disadvantages of failing to provide means for regulating the operational temperature of the carbon black generating surface, and fails to provide or suggest means for regulating the inlet air or outlet flue gases through a carbon black generating cylinder. Further, the prior art fails to provide or suggest a means for assuring efficient uniform production of the desired size carbon black material when ambient conditions, such as relative humidity and atmospheric pressure, change during operation.
Most importantly, the prior art fails to teach or suggest means of rotatably mounting a carbon black generating cylinder on bearing surfaces, whereby the bearing surfaces are thermally insulated from the hot working area of the rotating cylinder.